1. Field of the Invention
The present invention relates to a vibration analysis device which calculates a cycle of vibration of a tool with respect to a workpiece.
2. Description of the Related Art
A machine tool can perform processing while moving at least one of a workpiece (an object to be processed) or a tool along a predetermined drive axis. In other words, a machine tool can perform processing while changing a relative position between a workpiece and a tool. Since the relative position of the tool with respect to the workpiece changes during a processing period, it is preferable for a worker to grasp processing states, such as a velocity of the tool with respect to the workpiece.
Japanese Patent No. 5302371 discloses a numerical control device for a machine tool, which can display physical data of velocities of a drive axis in the machine tool and a representative point of a tool, with reference to a movement distance of the tool. It is disclosed that, in this device, by converting physical data as a function of time into physical data as a function of movement distance, the physical data can be compared at the same processing position even under processing conditions where the velocities and the like are different.
During a period in which a workpiece is processed, a relative position of a tool with respect to the workpiece changes in a state where the tool is in contact with the workpiece. At this time, vibration of a device mounted in the machine tool can be transmitted to a spindle head holding the tool and a table holding the workpiece. Due to this, the workpiece and the tool can vibrate. For example, a fan motor mounted in an inverter or the like can vibrate. Alternatively, vibration can be transmitted from a machine outside the machine tool. When the tool and the workpiece vibrate due to vibration transmitted from such a vibration source, a streak pattern can occur on a processed surface of the workpiece. In other words, streaks can occur at predetermined intervals.
Such a streak pattern is formed depending on a vibration cycle of the tool with respect to the workpiece and a relative velocity of the tool with respect to the workpiece. It is preferable for a worker to be able to also grasp the cycle of vibration which causes occurrence of the streak pattern. However, a machine tool can perform processing while changing the relative velocity of the tool with respect to the workpiece. During a processing period, the velocity of a processing point changes. In this case, the interval between streaks is uneven, and therefore there has been a problem in that it is difficult to calculate the cycle of vibration of the tool with respect to the workpiece.